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Date: Sat, 11 May 2013 09:06:11 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Seeking for papers about tagged types vs access to subprograms
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Date: 2013-05-11T09:05:56+02:00
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On 11.05.13 08:37, Dmitry A. Kazakov wrote:
> First of all, there are preconditions of operations and the precondition
> put on individual calls. I don't know which one you mean here. But the
> preconditions of operations must be statically true. Meaning: a declared
> operation can be called anywhere. The client may annotate his calls to the
> operation with additional preconditions related to the logic of the program
> that uses the operation. These are not the property of the operation and
> unrelated to the type.
>
> The idea that the precondition of first kind should depend on the state of
> the objects involved in the operation is a very, VERY bad idea.

How do you specify the preconditions of the second kind (on individual
calls) in such a way that a programmer, wishing to calling these operations,
ensures the calls won't fail as a consequence of violating these
preconditions?